Directly injecting fuel into an engine cylinder may improve some engine operation in ways that injecting fuel into a cylinder's intake port does not improve engine operation. Likewise, injecting fuel into a cylinder's intake port may improve engine operation in ways that directly injecting fuel into an engine cylinder does not improve engine operation. For example, during lower engine loads, port fuel injection may be preferred over direct fuel injection because port fuel injectors are quieter than direct fuel injectors. On the other hand, direct fuel injectors may be operated at higher engine loads to reduce the possibility of engine knock since directly injecting fuel into a cylinder cools the cylinder charge via fuel vaporization. Advantages of port fuel injection and direct fuel injection maybe realized by incorporating port and direct fuel injection into an engine. However, during conditions where the direct fuel injectors are deactivated, the direct injection fuel pump may continue to operate such that engine fuel economy is less than is desired.
The inventors herein have recognized the above-mentioned issue may be at least partly addressed by a method of operating a direct injection fuel pump, comprising: during a first condition, operating a direct injection fuel pump with a first piston lift amount; and during a second condition, the second condition different from the first condition, operating the direct injection fuel pump with a second piston lift amount, the second piston lift amount greater than the first piston lift amount.
By operating a direct injection fuel pump with varying lift amounts, it may be possible to deactivate the direct injection fuel pump and use less energy in doing so. For example, the direct injection fuel pump may transition from a low lift cam profile to zero lift cam profile to deactivate the direct injection fuel pump. The fuel pump piston may remain stationary when operated with a zero lift cam profile. Therefore, the direct injection fuel pump is not consuming energy by compressing fuel in the direct injection fuel pump's compression chamber. Additionally, since the piston is stationary and not reciprocating, the direct injection fuel pump may not require lubrication.
The present description may provide several advantages. For example, the approach may reduce fuel consumption of an engine. Additionally, the approach may be applied using a compact mechanism. Further, the approach may allow the engine to rotate without providing lubrication to the direct fuel injection pump piston and pumping chamber.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.